Transmission issue - Selecting D, 2, or L not selecting the correct gear range

[Mad Matt]

I've got a 1996 FZJ80 with 216k on the clock, and here is the issue, when manually selecting "2" or "L" on the transmission, it no longer selects the expected gear. Here is what it is doing

• Gear Selected = Outcome
• "D" + OD on = performs as expected (4th gear w/ OD)
• 'D" + OD off = performs as expected (4th gear w/o OD)
• "2" + OD on = turns off OD
• "2" + OD off = functions as if the transmission was put into "2"
• "L" + OD on = functions as if the transmission was put into "2"
• "L" + OD off = depending on if I am using the throttle, the transmission will either go from "2" to "L"
  • "L" + OD off + accelerator = functions as if the transmission was put into "2"
  • "L" + OD off + no accelerator = functions as if the transmission was put into "L"

I am getting a P1780 code that indicates "A/T indicator switch" or "Park/Neutral Position Switch" Malfunction. I took it to Cascade Cruisers, and they replaced the Park/Neutral Position Switch" and adjusted the linkage, but they could never figure out how to fix the error code or shifting problem. My cruise control also stopped working at the same time, so I am assuming this is related.

Any guidance on what I should check next would be a huge help. Thanks!

 

[JoeCova]

I've got a 1996 FZJ80 with 216k on the clock, and here is the issue, when manually selecting "2" or "L" on the transmission, it no longer selects the expected gear. Here is what it is doing

• Gear Selected = Outcome
• "D" + OD on = performs as expected (4th gear w/ OD)
• 'D" + OD off = performs as expected (4th gear w/o OD)
• "2" + OD on = turns off OD
• "2" + OD off = functions as if the transmission was put into "2"
• "L" + OD on = functions as if the transmission was put into "2"
• "L" + OD off = depending on if I am using the throttle, the transmission will either go from "2" to "L"
  • "L" + OD off + accelerator = functions as if the transmission was put into "2"
  • "L" + OD off + no accelerator = functions as if the transmission was put into "L"

I am getting a P1780 code that indicates "A/T indicator switch" or "Park/Neutral Position Switch" Malfunction. I took it to Cascade Cruisers, and they replaced the Park/Neutral Position Switch" and adjusted the linkage, but they could never figure out how to fix the error code or shifting problem. My cruise control also stopped working at the same time, so I am assuming this is related.

Any guidance on what I should check next would be a huge help. Thanks!

Unless there is some new transmission design I am completely ignorant of, 4th gear is overdrive so turning it off just means you wont shift into 4th.

If you shift to L or 2 the only way it wouldn’t be is if the linkage is off.

Could be a wiring issue

 

[Malleus]

It sounds like a pressure problem. Here's the shift strategy (in theory, anyway):

 

[Malleus]

The transmission has two pressure controls: line pressure and throttle pressure. The line pressure acts on the pistons and performs the shifts, the throttle pressure controls the line pressure (via the throttle cable on the right side of the engine).

The shift pistons are located between the valve body and the underside of the case:

 

[Malleus]

If either the valve body or pistons are leaking, you'll experience shift problems. Without knowing more about the history, and frankly without seeing/feeling/hearing, it's tough to give any meaningful suggestions. Here are some things that might help your shop:

All of this is in the transmission FSM (RM479U). If they don't have one, have them get one; there's a copy in the Resources section. The troubleshooting matrix section is attached for your use.

FYI, there are two A343F FSMs in the Resources section. RM479U is the transmission repair manual which covers on-vehicle repair and removal/installation. There is a "A340F/A343F" FSM in there also; this one is for teardown, overhaul and rebuild. You don't want that one. It doesn't make for light reading, but it is interesting.

 

[Malleus]

I should have mentioned, because there's a note in the post above, the TCM (which is really what's referred to when the ECM is cited above) is incorporated in the ECM enclosure, unlike the '93-'94 80 series which have separate ECM and TCM.

Having said all that, the ECM test values, as they pertain to the transmission, are in the transmission FSM (RM479U). I mention this because there is also an ECM section in the engine chapter of the other 80 series FSM (RM432U). That ECM troubleshooting section contains only engine related ECM values.